In general, an aircraft has a body, a right wing, a left wing, a front landing gear assembly provided at the front lower portion of the body, a right wing landing gear assembly provided at the lower portion of the right wing, and a left wing landing gear assembly provided at the lower portion of the left wing. Each of the front landing gear assembly, the right wing landing gear assembly and the left wing landing gear assembly is hereinafter simply referred as "a landing gear" and generally comprises rubber wheels and an arm having the rubber wheels rotatably supported at the lower end portion thereof.
The landing gear is designed to be retracted into the body of the aircraft while it is flying at a cruising speed and to be extended from the body of the aircraft when it is landing and taking off and while it is moving on land. The reason why the landing gear is being retracted into the body of the aircraft while it is flying at a cruising speed is that the landing gear is liable to affect the flying performance of the aircraft such as cruising speeds and distances caused by air resistance of the landing gear. For this reason, the landing gear is required to be retracted into the body of the aircraft and extended from the body of the aircraft.
The landing gear of this type is generally operated by a hydraulic system which comprises a driving motor, a hydraulic pump driven by the driving motor, an actuator operatively connected to the landing gear and reciprocably moved by the hydraulic pump to retract the landing gear into the body of the aircraft and to expand the landing gear from the body of the aircraft with a hydraulic fluid supplied to the actuator and discharged from the actuator by the hydraulic pump, a hydraulic fluid reservoir for reserving the hydraulic fluid, a change-over valve for selectively changing the flow of the hydraulic fluid to supply the actuator with the hydraulic fluid and to discharge the hydraulic fluid from the actuator, and locking means for locking the landing gear with and unlocking the landing gear from the body of the aircraft when it is held at its retracted and extended positions.
There have so far been proposed various types of hydraulic systems one of which comprises a driving motor, a hydraulic pump driven by the driving motor, three sets of actuators for operating the landing gears of the front landing gear assembly, the right wing landing gear assembly and the left wing landing gear assembly, three sets of change-over valves each provided between the hydraulic pump and each of the actuators to selectively change the flow of the hydraulic fluid between the hydraulic pump and the actuator, and three sets of locking means each provided with each of the actuators to lock and retain the actuator at its retracted and extended position. The three sets of the actuators, change-over valves and locking means are arranged in separated and spaced relationship with each other and thus operatively connected by hydraulic pipes leading to only one hydraulic pump. The assembling of these parts for producing such an aircraft requires time-consuming and laborious works. This results in increasing overall expenses in production for aircraft.
It is therefore an object of the present invention to provide a hydraulic system which comprises a driving motor, a hydraulic pump, an actuator, a change-over valve, and locking means all of which are accommodated in a single housing unit with no hydraulic pipes needed for the conventional hydraulic systems.
It is another object of the present invention to provide a hydraulic system which does not require time-consuming and laborious works with no need for the above parts assembled with one another.
It is a further object of the present invention to provide a hydraulic system which can reduce overall expenses in production for an aircraft.